JP6900837B2 - Oxidized ore smelting method, reduction furnace - Google Patents

Description

The present invention relates to a smelting method for oxide ore, for example, a smelting method for obtaining a reduced product by reducing nickel oxide ore or the like as a raw material with a carbonaceous reducing agent, and a reduction furnace used for the reduction treatment thereof. Regarding.

As a method for smelting nickel oxide ore called limonite or saprolite, which is a type of oxide ore, a pyrometallurgical method for producing nickel mats using a smelting furnace, iron and nickel using a rotary kiln or a mobile hearth furnace. There are known pyrometallurgical methods for producing ferrometallurgy, which is an alloy of the above, and wet smelting methods for producing mixed smelted using an ore.

Among the various methods described above, especially when the nickel oxide ore is reduced and smelted by using a pyrometallurgical method, the raw material nickel oxide ore is crushed to an appropriate size in order to proceed with the reaction. The process of agglomerating is performed as a pretreatment.

Specifically, when the nickel oxide ore is agglomerated, that is, when the powdery or finely granular ore is agglomerated, the nickel oxide ore is mixed with other components, for example, a reducing agent such as a binder or coke. After the water content is adjusted, the mixture is charged into a lump manufacturing machine, and for example, a lump (pellet, briquette, etc.) having a side or a diameter of about 10 mm to 30 mm is simply referred to as "pellet". ) Is common.

The pellets obtained in the form of agglomerates need to have a certain degree of air permeability in order to "fly" the contained moisture. Further, if the reduction does not proceed uniformly in the pellets in the subsequent reduction treatment, the composition of the obtained reduced product becomes non-uniform, causing inconveniences such as metal being dispersed or unevenly distributed. Therefore, it is important to mix the mixture uniformly when preparing the pellets and to maintain the temperature as uniform as possible when reducing the obtained pellets.

In addition, coarsening the metal (ferronickel) produced by the reduction treatment is also a very important technique. When the produced ferronickel has a fine size of, for example, several tens of μm to several hundreds of μm or less, it becomes difficult to separate it from the slag produced at the same time, and the recovery rate (yield) as ferronickel is greatly reduced. It ends up. Therefore, a treatment for coarsening the reduced ferronickel is required.

For example, Patent Document 1 discloses a technique relating to a method for producing ferronickel, and uses a raw material containing nickel oxide and iron oxide as a pretreatment when producing ferronickel using a mobile hearth furnace. Disclosed is a technique for producing pellets while adjusting the amount of excess carbon in the mixture in a mixing step of mixing with a carbonaceous reducing agent to form a mixture, and charging the pellets into a furnace to perform a reduction step. There is.

Here, in Patent Document 1, a mixer may be used to mix the raw material and the carbonaceous reducing material, and the obtained mixture may be charged into the mobile hearth furnace as it is, but it is agglomerated by the granulator. It is preferable to agglomerate, and by agglomerating in this way, the amount of dust generated from the mobile hearth furnace and the melting furnace is reduced, and the heat transfer efficiency inside the agglomerate (mixture) in the mobile hearth furnace is reduced. Is described in that the reduction rate is increased. Further, it is described that the granulated agglomerates (mixtures) are charged into a mobile hearth furnace and heated at an atmospheric temperature of 1000 to 1400 ° C. for reduction.

However, although Patent Document 1 describes that the mixture may be charged into the mobile hearth furnace as it is, the melting point of the slag of nickel oxide ore is generally about 1300 ° C to 1400 ° C, and Since a metal hearth is used in a mobile hearth furnace, it is considered impossible to smelt nickel oxide ore because the hearth reacts with the molten slag. That is, in the reduction of the mixture, it is required that the hearth and the slag do not react.

Further, when the reduced mixture is recovered as it is to separate the slag and the metal, if the metal is too small, it becomes difficult to separate the slag and the metal. Therefore, for example, it is necessary to hold the reduced mixture in a semi-molten state or a molten state to effectively coarsen the metal.

In such a case, it is necessary to uniformly cause a reduction reaction with respect to the mixture in the reduction furnace. In order to generate coarse metal and uniformly separate slag and metal, it is important to make the reaction temperature and the atmosphere in the furnace uniform. However, when the obtained reactant (reduced product) is taken out from the reduction furnace after the reduction, if it takes a long time to take out the reaction product (reduced product), uneven metal formation occurs, and as a result, the composition and size are non-uniform. May become metal.

Further, for example, when a mechanical extraction mechanism is provided in the reduction furnace, durability at high temperatures is required, which complicates the structure and affects the life of the equipment, resulting in an increase in cost. There is. Furthermore, air may be mixed through the gap between the take-out mechanism and the reduction furnace body, and the atmosphere inside the furnace may change to affect the reduction reaction, which may cause variations in quality.

In addition, when a reduction furnace having a mobile hearth such as a rotary furnace is used in order to improve productivity, there is a problem that equipment gaps and time required for taking out are increased, and a uniform reaction occurs. It is not easy to obtain a metal having a uniform composition and size. It should be noted that the installation of the rotary hearth furnace requires a large area, and further, since the entire structure is rotated, a large amount of power is required in the operation, and there is also a problem that the operation cost increases.

In this way, when an oxide ore such as nickel oxide ore is mixed and the mixture is reduced to produce a metal, the metal effectively coarsened by the reduction is efficiently recovered, and high-quality metal is produced without variation. There were many problems in manufacturing.

Japanese Unexamined Patent Publication No. 2004-156140

The present invention has been proposed in view of such circumstances, and efficiently recovers metal in a smelting method for producing metal by reducing a mixture containing oxide ore such as nickel oxide ore. It is an object of the present invention to provide a method capable of producing high-quality metal with little variation in quality.

As a result of diligent studies, the present inventor uses a reduction furnace provided with a hearth having an opening / closing structure, and opens the hearth when transferring a product (for example, a reduced product) obtained after the reduction treatment. By doing so, it was found that the above-mentioned problems could be solved by transferring the reduced product downward, and the present invention was completed.

(1) The first invention of the present invention is a method for smelting an oxide ore in which a mixture obtained by mixing an oxide ore and a carbonaceous reducing agent is charged into a reduction furnace and subjected to a reduction treatment in the reduction furnace. The reduction furnace is provided with a hearth having an opening / closing structure, and the mixture is reduced on the hearth with the opening / closing structure closed, and the mixture is obtained after the reduction treatment is completed. This is a method for smelting oxidized ore, in which the product is transferred from the hearth by opening the opening / closing structure.

(2) In the second invention of the present invention, in the first invention, the reduction furnace is provided with a plurality of stages of processing chambers in the height direction, and the hearth of each of the processing chambers has the opening / closing structure. Of the oxide ore, which is a hearth, and after the reduction treatment in the upper treatment chamber is completed, the obtained product is transferred to the lower treatment chamber by opening the opening / closing structure of the hearth of the treatment chamber. It is a smelting method.

(3) The third invention of the present invention is the method for smelting oxidized ore in the first or second invention, in which the reduction temperature in the reduction treatment is 1200 ° C. or higher and 1450 ° C. or lower.

(4) The fourth invention of the present invention is a method for smelting an oxide ore, which is a nickel oxide ore in any one of the first to third inventions.

(5) A fifth invention of the present invention is, in any one of the first to fourth inventions, a method for smelting an oxide ore in which the product contains ferronickel.

(6) The sixth invention of the present invention is a reduction furnace for performing a reduction treatment on a mixture obtained by mixing an oxide ore and a carbonaceous reducing agent, and the mixture is placed and opened / closed. The mixture is subjected to a reduction treatment on the hearth having a structure and the opening / closing structure is closed, and after the reduction treatment is completed, the obtained product is opened by opening the opening / closing structure. It is a reduction furnace that is transferred from the hearth.

According to the present invention, in a smelting method for producing a metal by reducing a mixture containing an oxide ore such as a nickel oxide ore, the metal can be efficiently recovered, and the quality is high with little variation in quality. Metal can be manufactured.

It is a process drawing which shows an example of the flow of the smelting method of nickel oxide ore. It is sectional drawing which shows an example of the structure of a reduction furnace. It is sectional drawing which shows an example of the structure of a reduction furnace.

Hereinafter, specific embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention. Further, in the present specification, the notation "X to Y" (X and Y are arbitrary numerical values) means "X or more and Y or less".

≪1. Outline of the present invention ≫
In the method for smelting an oxidized ore according to the present invention, an oxidized ore is used as a raw material, and the oxide ore and a carbonaceous reducing agent are mixed to form a mixture, and the obtained mixture is subjected to a reduction treatment at a high temperature to reduce the product. It is a method of manufacturing the metal. For example, as an oxide ore, nickel oxide ore containing nickel oxide, iron oxide, etc. is used as a raw material, and the nickel oxide ore is mixed with a carbonaceous reducing agent to preferentially reduce nickel contained in the mixture at a high temperature. Further, there is a method of producing ferronickel, which is an alloy of iron and nickel, by partially reducing iron.

Specifically, as the method for smelting oxide ore according to the present invention, a reduction furnace having a hearth having an opening / closing structure is used. Then, the mixture is reduced on the hearth with the opening / closing structure closed, and after the reduction treatment is completed, the obtained product is transferred from the hearth by opening the opening / closing structure.

According to such a smelting method, for example, a reduced product, which is a purified product obtained by a reduction treatment on a predetermined hearth, can be discharged from the hearth by opening the opening / closing structure of the hearth. The reduced product can be discharged as if it were naturally dropped, and all the reduced products can be recovered at once. That is, the time for taking out the reduced product from the reduction furnace can be shortened. As a result, the variation in quality is reduced, and high-quality metal can be stably recovered. Further, according to such a method, the coarsened metal can be effectively recovered, and according to such a metal, it becomes easy to sort the slag and the metal can be recovered efficiently.

Further, in such a smelting method, as the reduction furnace, a plurality of treatment chambers (reduction treatment chambers) are provided in the height direction, and the hearth of each treatment chamber is composed of a hearth having an opening / closing structure. After the reduction treatment in the upper processing chamber is completed, the obtained product is transferred to the lower processing chamber by opening the opening / closing structure of the hearth of the processing chamber. be able to. In this way, even when a plurality of treatment chambers are provided, the transfer of the product from the upper treatment chamber to the lower treatment chamber can be executed at once, and the variation in the transfer between the treatment chambers can be eliminated. ..

Hereinafter, as a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”), a method for smelting nickel oxide ore will be described as an example. As described above, the nickel oxide ore as a smelting raw material contains at least nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ), and the nickel oxide ore is reduced as a smelting raw material. Therefore, an iron-nickel alloy (ferronickel) can be produced as a metal.

The present invention is not limited to nickel oxide ore as an oxide ore, and the smelting method is not limited to a method for producing ferronickel from nickel oxide ore containing nickel oxide or the like.

≪2. Nickel oxide ore smelting method ≫
In the method for smelting nickel oxide ore according to the present embodiment, nickel oxide ore is mixed with a carbonaceous reducing agent to form a mixture, and the mixture is subjected to a reduction treatment to obtain ferronickel, which is a metal as a reduced product. And slag. Ferronickel, which is a metal, can be recovered by separating the metal from a mixture containing the metal and slag obtained through the reduction treatment.

FIG. 1 is a process diagram showing an example of a flow of a method for smelting nickel oxide ore. As shown in FIG. 1, in this smelting method, a mixing treatment step S1 for mixing raw materials containing nickel oxide ore, a mixture molding step S2 for molding the obtained mixture into a predetermined shape, and a molded mixture ( It has a reduction treatment step S3 in which pellets) are reduced and heated at a predetermined reduction temperature, and a separation step S4 in which the metal and slag produced in the reduction treatment step S3 are separated and the metal is recovered.

<2-1. Mixing process>
The mixing treatment step S1 is a step of mixing raw material powders containing nickel oxide ore to obtain a mixture. Specifically, in the mixing treatment step S1, a carbonaceous reducing agent is added to the nickel oxide ore which is a raw material ore and mixed, and as an additive of an optional component, iron ore, a flux component, a binder and the like, for example, Powders having a particle size of about 0.1 mm to 0.8 mm are added and mixed to obtain a mixture. The mixing process can be performed using a mixer or the like.

The nickel oxide ore as a raw material ore is not particularly limited, but limonite ore, saprolite ore and the like can be used. The nickel oxide ore contains at least nickel oxide (NiO) and iron oxide (Fe ₂ O _3).

The carbonaceous reducing agent is not particularly limited, and examples thereof include coal powder and coke powder. It is preferable that the carbonaceous reducing agent has a size equivalent to the particle size and particle size distribution of the nickel oxide ore, which is a raw material ore, because it is easy to mix uniformly and the reduction reaction is likely to proceed uniformly.

The mixed amount of carbonaceous reducing agent is the chemical equivalent required to reduce the total amount of nickel oxide constituting nickel oxide ore to nickel metal, and the chemical equivalent required to reduce iron oxide (ferrous oxide) to metallic iron. When the total value of both chemical equivalents (also referred to as "total value of chemical equivalents" for convenience) is 100% by mass, the ratio of carbon content of 5% by mass or more and 60% by mass or less is preferable, and more preferably. The ratio of the carbon content can be adjusted to be 10% by mass or more and 40% by mass or less. In this way, by setting the mixing amount of the carbonaceous reducing agent to a ratio of 5% by mass or more with respect to the total value of 100% by mass of chemical equivalents, the reduction of nickel can be efficiently promoted and the productivity can be improved. improves. On the other hand, by setting the ratio to 60% by mass or less with respect to the total value of 100% by mass of chemical equivalents, it is possible to suppress the reduction amount of iron, prevent deterioration of nickel grade, and produce high quality ferronickel. it can. As described above, preferably, the mixing amount of the carbonaceous reducing agent is set to the ratio of the carbon content of 5% by mass or more and 60% by mass or less to the total value of 100% by mass of the chemical equivalents, so that the metal component on the surface of the mixture It is preferable that the shell (metal shell) produced by the above method can be uniformly generated to improve the productivity, and high-quality ferronickel having a high nickel grade can be obtained.

Further, as the iron ore as an additive of an arbitrary component, for example, iron ore having an iron grade of about 50% or more, hematite obtained by hydrometallurgy of nickel oxide ore, or the like can be used.

Moreover, as a flux component, for example, calcium oxide, calcium hydroxide, calcium carbonate, silicon dioxide and the like can be mentioned. Examples of the binder include bentonite, polysaccharides, resins, water glasses, dehydrated cakes and the like.

In the mixing treatment step S1, a mixture is obtained by uniformly mixing the raw material powder containing the nickel oxide ore as described above. At the time of this mixing, kneading may be performed at the same time in order to improve the mixing property, or kneading may be performed after mixing. Specifically, kneading can be performed using, for example, a twin-screw kneader, and by kneading the mixture, a shearing force is applied to the mixture to disaggregate the carbonaceous reducing agent, the raw material powder, and the like, and the mixture is uniform. It is possible to improve the adhesion of each particle and reduce the voids. As a result, the reduction reaction is likely to occur and the reaction can be made uniform, and the reaction time of the reduction reaction can be shortened. Moreover, the variation in quality can be suppressed. As a result, highly productive treatment can be performed and high quality ferronickel can be produced.

Further, after kneading, it may be extruded using an extruder. By extruding with an extruder in this way, a higher kneading effect can be obtained.

Table 1 below shows an example of the composition (% by weight) of some of the raw material powders to be mixed in the mixing treatment step S1, but the composition of the raw material powders is not limited to this.

<2-2. Mixture molding process>
The mixture molding step S2 is a step of molding the mixture obtained in the mixing treatment step S1. Specifically, the mixture obtained by mixing the raw material powders is formed into lumps (lumps, hereinafter also referred to as "pellets") having a certain size or larger. Therefore, the mixture molding step S2 can be paraphrased as a pellet manufacturing step.

The molding method is not particularly limited, but an amount of water required for agglomerating the mixture is added, and for example, a bulk product manufacturing apparatus (rolling granulator, compression molding machine, extrusion molding machine, etc., or pelletizer) is also used. ) Is used to form pellets of a predetermined shape.

The shape of the pellet obtained by molding the mixture can be, for example, spherical, rectangular parallelepiped, cubic, columnar or the like. With such a shape, the mixture can be easily molded and the cost required for molding can be suppressed. Further, since the above-mentioned shape is a simple shape and is not complicated, the occurrence of defective products can be suppressed, and the quality of the obtained pellets can be made uniform.

Further, as for the shape of the pellet, it is preferable that the pellet can be processed in a laminated state in the treatment in the reduction treatment step of the next step, and in that respect as well, the pellet has a spherical shape, a rectangular parallelepiped shape, a cubic shape, a columnar shape, or the like. If there is, it is easy to stack and place it in the reduction furnace, and the amount of processing to be applied to the reduction treatment can be increased. Further, by laminating in this way and subjecting it to the reduction treatment, it is possible to increase the amount of treatment at the time of reduction without enlarging one pellet, so that it is easy to handle and it may collapse during movement or the like. It is possible to suppress the occurrence of defects and the like.

The size of the pellet is not particularly limited, but when it is spherical, it can be molded so that its diameter is about 10 mm to 30 mm. Further, in the case of a rectangular parallelepiped shape, a cube shape, a columnar shape, or the like, it can be molded so that the vertical and horizontal internal dimensions are approximately 500 mm or less. By molding into pellets having a size like these, the reduction treatment is uniformly applied, and smelting with less variation and high productivity can be performed.

After molding the mixture, the mixture may be subjected to a drying treatment. A predetermined amount of water may be contained in the mixture, and if the water inside is vaporized at once due to a rapid temperature rise during the reduction treatment and expands, there is a concern that the mixture will be shattered. From the viewpoint of preventing such expansion, a step of applying a drying treatment to the molded mixture can be provided.

Specifically, in the drying treatment, for example, the treatment can be performed so that the solid content of the pellets is about 70% by weight and the water content is about 30% by weight. For example, hot air at 150 ° C. to 400 ° C. is blown onto the pellets to dry them.

In the case of relatively large pellets, the mixture before and after the drying treatment may have cracks or cracks. When the lump is large, even if the surface area is increased due to cracking or the like, the effect is small and does not pose a big problem. Therefore, there is no particular problem even if the molded pellets subjected to the reduction treatment have cracks or the like.

Table 2 below shows an example of the composition (parts by weight) in the solid content of the mixture after the drying treatment. The composition of the mixture is not limited to this.

<2-3. Reduction process>
(1) Reduction Treatment In the reduction treatment step S3, the mixture formed through the mixture molding step S2 is charged into the reduction furnace and heated at a predetermined reduction temperature to perform the reduction treatment. By the reduction treatment in the reduction treatment step S3, the smelting reaction (reduction reaction) proceeds, and metal and slag, which are reduced products, are produced.

Specifically, the reduction treatment in the reduction treatment step S3 is performed using a reduction furnace, and the mixture (pellets) containing nickel oxide ore is reduced and heated by charging the mixture (pellets) containing nickel oxide ore into a reduction furnace heated to a predetermined reduction temperature. .. In the reduction treatment using a reduction furnace, the nickel oxide contained in the nickel oxide ore, which is the raw material ore, is reduced as completely preferentially as possible, while the iron oxide contained in the nickel oxide ore is partially reduced. Then, so-called partial reduction is performed to obtain the desired high nickel grade ferronickel.

In the reduction treatment, for example, in a short time of about 1 minute, the nickel oxide ore and iron oxide in the mixture are first reduced and metallized in the vicinity of the surface of the pellet where the reduction reaction easily proceeds, and the iron-nickel alloy (hereinafter referred to as iron-nickel alloy) is formed. The nickel alloy is also called "ferronickel") and forms a shell. On the other hand, in the shell, the slag component in the container is gradually melted with the formation of the shell to generate liquid phase slag. As a result, ferronickel metal (hereinafter, simply referred to as “metal”) and ferronickel slag (hereinafter, simply referred to as “slag”) are separately produced in the mixture.

Further, when the mixture is sufficiently mixed and there is substantially no composition variation, the raw materials are in close contact with each other, so that the reduction reaction occurs uniformly. Therefore, it is not necessary to generate a metal shell as conventionally said, and to react and homogenize it over a certain period of time, and therefore it is not essential to generate a metal shell. That is, even if a metal shell cannot be formed, the reaction proceeds uniformly, and ferronickel can be produced.

In the reduction treatment step S3, the slag in the mixture is melted into a liquid phase, but the metal and the slag that have already been separated and produced by the reduction treatment do not mix with each other, and the metal solid phase is obtained by the subsequent cooling. And the slag solid phase are mixed as separate phases. The volume of this mixture is reduced to about 50% to 60% of the volume of the mixture to be charged.

The temperature (reduction temperature) in the reduction treatment is not particularly limited, but is preferably in the range of 1200 ° C. or higher and 1450 ° C. or lower, and more preferably in the range of 1300 ° C. or higher and 1400 ° C. or lower. By reducing in such a temperature range, a uniform reduction reaction can be generated, and ferronickel with suppressed quality variation can be produced. Further, more preferably, by reducing at a reduction temperature in the range of 1300 ° C. or higher and 1400 ° C. or lower, a desired reduction reaction can be generated in a relatively short time.

In the reduction treatment, the internal temperature of the reduction furnace is raised by a burner or the like until the reduction temperature reaches the above-mentioned range, and the temperature is maintained after the temperature rise.

(2) Configuration of reduction furnace (first form)
FIG. 2 is a cross-sectional view of a reduction furnace used for the reduction treatment, and shows an example of the configuration. The reduction furnace 1 includes a charging inlet 11 for charging the pellet P to be reduced into the furnace space S, and a discharge port 12 for discharging the reduced product obtained by the reduction treatment to the outside of the furnace.

Further, the reduction furnace 1 is provided with a hearth 13 having an opening / closing structure inside. The hearth 13 and the furnace wall 14 of the reduction furnace 1 are preferably made of refractory bricks.

More specifically, the reduction furnace 1 is provided with a hearth 13 having a predetermined opening / closing structure, instead of a fixed hearth fixed to a conventional general reduction furnace. The charged pellet P is placed on the hearth 13, and the pellet P is subjected to a reduction treatment to become a product (for example, a reduced product). The hearth 13 is composed of an opening / closing structure, and by opening the opening / closing structure, the obtained product is naturally dropped by gravity.

The opening / closing structure of the hearth 13 is not particularly limited, but as shown in FIG. 2, for example, a sliding structure is used in which a plate-shaped hearth is slid to open / close in the horizontal direction (direction of arrow F in FIG. 2). be able to. Further, although not shown, the hearth may be composed of two plate-shaped bodies, and the two plate-shaped bodies may be opened or closed in a double-door manner by a piston or the like.

The hearth 13 is preferably made of a material having excellent heat resistance, and is preferably made of refractory bricks. If at least the hearth 13 is a reduction furnace 1 made of refractory bricks, it can withstand temperature conditions of 1500 ° C. or higher, and the reduction temperature (temperature at which the mixture is melted) can be raised to, for example, about 1450 ° C. it can. By performing the reduction treatment under such a reduction temperature condition, the reduction reaction time can be shortened. Also. The generated metal is settled and easily coarsened, which facilitates the separation of the slag and the metal, and the metal can be recovered even more efficiently. Further, since the hearth 13 is made of refractory bricks, it is possible to prevent the pellet P in contact with the hearth 13 from reacting with the hearth 13, and it is possible to suppress welding of the pellet P and the like. Can be done. This facilitates the recovery work of the obtained reduced product and can efficiently recover the coarse metal.

The furnace wall 14 of the reduction furnace 1 is also preferably made of refractory bricks.

The reduction furnace 1 is heated to a temperature (reduction temperature) of, for example, about 1200 ° C. to 1450 ° C., and pellets P are charged into the heated furnace space S via the charging inlet 11. In the reduction furnace 1, the pellet P placed on the hearth 13 is subjected to a reduction treatment in a predetermined reduction time. At the time of the reduction treatment, the hearth 13 having the opening / closing structure is in a closed state, and the pellet P placed on the hearth 13 and existing in the furnace space S is treated.

(Second form)
As a modification, the reduction furnace 1'as shown in FIG. 3 can be used. Specifically, the reduction furnace 1'is provided with a plurality of treatment chambers (reduction treatment chambers) 20 (20a, 20b) in the height direction, and the hearth 13 (13a, 13b) of each treatment chamber 20 is provided. Is composed of a hearth having an opening / closing structure. Note that FIG. 3 shows an example in which two processing chambers, an upper processing chamber 20a and a lower processing chamber 20b, are provided, but the present invention is not limited to this.

In such a reduction furnace 1', for example, the heating temperature in each processing chamber 20 can be set to a different temperature, and the stepwise reduction treatment can be performed at different reduction temperatures. Specifically, the reduction temperature of the lower processing chamber 20b and the furnace space S2 is set higher than the furnace space S1 of the upper processing chamber 20a, and the reduction treatment for the pellet P is performed stepwisely and continuously at different temperatures. Can be done.

Further, the upper treatment chamber 20a may be used as a preheat treatment chamber to perform the preheat treatment before the reduction treatment. Alternatively, the upper treatment chamber 20a is used as a reduction treatment chamber, the lower treatment chamber 20b is used as a temperature holding chamber, and the metal in the reduced product obtained by the reduction treatment in the treatment chamber 20a grows in the lower treatment chamber 20b. It may be subjected to a process of making it coarse.

As in these examples, by providing the processing chambers 20 having a plurality of stages in the height direction, continuous processing can be performed in the vertical direction.

In the reduction furnace 1', the hearth 13 provided in each processing chamber 20 is a hearth 13 having an opening / closing structure. The pellet P is treated with the opening / closing structure of the hearth 13 closed. Then, when the obtained product is transferred after the predetermined treatment, the obtained product is naturally dropped by gravity by opening the opening / closing structure of the hearth 13.

The opening / closing structure of the hearth 13 (13a, 13b) provided in each of the processing chambers 20 (20a, 20b) is the horizontal direction (arrows F1 direction and F2 direction in FIG. 3) as in the first embodiment. ) Can be slid to open and close the plate-shaped hearth.

(3) Recovery and transfer of reduced product For example, in the reduction furnace 1 as shown in FIG. 2, after the reduction treatment is completed, the obtained reduced product is discharged to the outside of the furnace through the discharge port 12. In the embodiment, by opening the hearth 13 having an opening / closing structure, the produced reduced product is naturally dropped in the direction of the discharge port 12 and discharged to the outside of the furnace. For example, when the opening / closing structure of the hearth 13 is a slide type, the hearth 13 is opened by sliding it in the horizontal direction after the reduction treatment, and the hearth 13 is discharged to the outside of the furnace.

By discharging the obtained reduced product by using the hearth 13 having an opening / closing structure and opening the hearth 13, the reduced product can be taken out at once, and the time required for taking out the reduced product. Can be shortened. If it takes a long time to take out the reduced product, the residence time of the reduced product in the reduction furnace 1 will vary, and uneven metal formation of the reduced product will occur, resulting in ferronickel having a uniform metal grade. It may not be possible to collect it. On the other hand, by using the hearth 13 having an opening / closing structure and taking out the obtained reduced products at once, all the reduced products can be discharged to the outside of the furnace in a short time and stay in the reduction furnace 1. Ferronickel having a uniform metal grade can be efficiently recovered by suppressing time variation.

Further, according to such a method, the coarsened metal can be efficiently recovered, and as a result, it becomes easy to sort the slag and the metal recovery rate can be increased.

Further, since the hearth 13 has an opening / closing structure, it is possible to suppress an increase in equipment cost and prevent a change in the atmosphere inside the furnace.

The temperature at the time of recovery of the reduced product is not particularly limited, but is preferably 1350 ° C. or lower, and more preferably 1250 ° C. or lower. By setting the recovery temperature to 1350 ° C. or lower in this way, the cost can be reduced and the reduced product can be efficiently recovered. In particular, by setting the recovery temperature to 1350 ° C. or lower, it is possible to maximize the reduction reaction and more efficiently suppress the welding of the reduced product to the hearth 13 due to the melting of the reduced product. Efficient collection work can be performed. The lower limit of the temperature at the time of recovery is preferably 1200 ° C. or higher.

Further, for example, in the reduction furnace 1'as shown in FIG. 3, after the completion of the predetermined treatment in the upper processing chamber 20a, the hearth 13a having an opening / closing structure is opened to generate the reduction furnace 20a. The product is naturally dropped and transferred to the processing chamber 20b located below. For example, when the opening / closing structure of the hearth 13a is a slide type, the hearth 13a is opened by sliding it in the horizontal direction after the reduction treatment, and is transferred to the lower processing chamber 20b.

Similarly, even after the reduction treatment in the lower processing chamber 20b is completed, by opening the hearth 13a of the opening / closing structure, the product (reduced product) produced in the processing chamber 20b is directed toward the discharge port 12. Drop it naturally and discharge it to the outside of the furnace.

In this way, even in the reduction furnace 1'provided with a plurality of processing chambers 20 in the height direction, the hearth 13 of each processing chamber 20 is configured by an opening / closing structure, and the obtained product is obtained. By transferring by opening the hearth 13, the product can be taken out at once, and the time required for taking out the reduced product can be shortened. Further, even when the continuous treatment is performed in the vertical direction, the purified product can be transferred at once, so that the treatment efficiency can be improved and stable continuous treatment can be performed.

<2-4. Separation process>
In the separation step S4, the metal and slag produced in the reduction treatment step S3 are separated and the metal is recovered. Specifically, the metal phase is separated and recovered from the mixture (mixture) containing the metal phase (metal solid phase) and the slag phase (slag solid phase) obtained by the reduction heat treatment of the mixture.

As a method for separating the metal phase and the slag phase from the mixture of the metal phase and the slag phase obtained as a solid, for example, in addition to removing unnecessary substances by sieving, separation by specific gravity, separation by magnetic force, etc. Method can be used.

Further, the obtained metal phase and slag phase can be easily separated due to poor wettability, and for example, a predetermined mixture can be obtained with respect to the large mixture obtained by the treatment in the reduction treatment step S3 described above. The metal phase and the slag phase can be easily separated from the mixture by giving an impact such as dropping with a head or giving a predetermined vibration at the time of sieving.

By separating the metal phase and the slag phase in this way, the metal phase is recovered.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to the following Examples.

<< Examples 1 to 6 and Comparative Examples 1 to 2 >>
[Mixing process]
An appropriate amount of nickel oxide ore as a raw material ore, iron ore, silica sand and limestone as flux components, a binder, and a carbonaceous reducing agent (coal powder, carbon content: 85% by weight, average particle size: about 190 μm). The mixture was obtained by mixing using a mixer while adding the water of. The carbonaceous reducing agent has a total value of 100% by mass, which is the total amount required to reduce _{nickel oxide (NiO) and iron oxide (Fe 2} O ₃ ) contained in nickel oxide ore, which is a raw material ore, in just proportion. When it was added, it was contained in an amount of 25%.

[Mixture molding process]
Next, the obtained mixture was granulated into a spherical shape using a pan-type granulator and sieved to a size of φ15.5 ± 1.5 mm.

[Reduction process]
Next, the prepared mixture samples (10 in each test) were charged into a reduction furnace, and the reduction treatment was performed at each reduction temperature and reduction time shown in Table 4 below. As the reduction furnace, a furnace having a structure as shown in FIG. 2 and having a hearth and a furnace wall made of refractory bricks was used.

Prior to the reduction treatment, each mixture sample to be subjected to the reduction treatment was dried by blowing hot air at 300 ° C. to 400 ° C. so that the solid content was about 70% by weight and the water content was about 30% by weight. Table 3 below shows the solid content composition (excluding carbon) of the sample after the drying treatment.

Specifically, in Examples 1 to 6, a reduction furnace provided with a hearth having an opening / closing structure as shown in FIG. 2 was used as the reduction furnace. The hearth of the reduction furnace was constructed of refractory bricks. During the reduction treatment, the mixture sample was treated with the hearth of the open / closed structure closed, and after the reduction treatment, the open / closed structure of the hearth was opened to discharge the sample to the outside of the furnace for recovery.

On the other hand, in Comparative Examples 1 and 2, a rotary hearth furnace, which is a conventional mobile hearth furnace, was used as the reduction furnace. After the reduction treatment using the rotary hearth furnace was completed, the reduced product was taken out along the guide provided in the furnace when the reduced product was collected. The hearth of the reduction furnace is made of metal, and in Comparative Examples 1 and 2, there is a high possibility that the hearth of the reduction furnace and the mixture sample are welded by the reaction and cannot be peeled off from the hearth, making recovery impossible. Therefore, ash (the main component is SiO ₂ and ash containing a small amount of oxides such _{as Al 2} O ₃ and Mg O as other components) is spread on the metal hearth to substantially contain oxidation. The mixture sample was charged in a no nitrogen atmosphere.

In all the test examples, after the reduced product was recovered, it was quickly cooled to room temperature while flowing nitrogen, and then taken out into the atmosphere.

≪Evaluation≫
For the sample taken out after the reduction heat treatment, the nickel metal ratio and the nickel content in the metal were analyzed and calculated by an ICP emission spectrophotometer (SHIMAZU S-8100 type). Table 4 below also shows the values calculated from the analysis results. The nickel metal ratio was calculated by the formula (1), and the nickel content in the metal was calculated by the formula (2), and the average of a total of 10 reduced products obtained for each test was calculated.
Nickel metal ratio = Amount of metallized Ni in the mixture ÷ (Amount of all Ni in pellets) × 100 (%) ・ ・ ・ Equation (1) Nickel content in metal = Amount of metallized Ni in the mixture ÷ (total amount of metallized Ni and Fe in pellets) × 100 (%) ・ ・ ・ Eq. (2)

As shown in the results of Table 4, in Examples 1 to 6, a reduction furnace provided with a hearth having an opening / closing structure is used, and when the reduced product is discharged, the reduced product is discharged by opening the hearth. Since it was moved in the direction of the outlet and discharged, the reduced product could be recovered efficiently, and the metal could be produced with high productivity. Further, the nickel metallization rate and the nickel content in the metal were both high values and good results were obtained, and high quality metal could be produced.

On the other hand, in Comparative Example 1, both the nickel metallization rate and the nickel content in the metal were lower than those in the example. It is considered that this is because it took a long time to take out the reduced product, so that the metal formation was uneven and uneven. Moreover, in Comparative Example 2, although the hearth was covered with ash, the metal hearth reacted with the mixture sample, and the reduced product could not be effectively recovered.

1,1'Reduction furnace 11 Inlet 12 Outlet 13, 13a, 13b Hearth 14 Furnace wall 20, 20a, 20b Processing room

Claims (5)

A method for smelting an oxide ore in which a mixture obtained by mixing an oxide ore and a carbonaceous reducing agent is charged into a reduction furnace and a reduction treatment is performed in the reduction furnace.
The reduction furnace has a plurality of processing chambers in the height direction, and the hearth of each of the processing chambers has an opening / closing structure.
The reduction treatment of the mixture is performed on the hearth of the processing chamber located above in a state where the opening / closing structure is closed, and after the reduction treatment is completed, the obtained product is subjected to the hearth of the treatment chamber. A method for smelting an oxide ore that is transferred to the processing chamber located below by opening the opening / closing structure of the above. The method for smelting an oxidized ore according to claim 1, wherein the reduction temperature in the reduction treatment is 1200 ° C. or higher and 1450 ° C. or lower. The method for smelting an oxide ore according to claim 1 or 2 , wherein the oxide ore is a nickel oxide ore. The method for smelting an oxidized ore according to any one of claims 1 to 3 , wherein the product contains ferronickel. A reduction furnace for reducing a mixture obtained by mixing an oxide ore and a carbonaceous reducing agent.
The reduction furnace has a plurality of processing chambers in the height direction, and the hearth of each of the processing chambers has an opening / closing structure.
The reduction treatment of the mixture is performed on the hearth of the processing chamber located above in a state where the opening / closing structure is closed, and after the reduction treatment is completed, the obtained product is subjected to the hearth of the treatment chamber. A reduction furnace that is transferred to the processing chamber located below by opening the opening / closing structure of the above.

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